The present invention relates to methods and apparatus for cleaning oil and dirt contaminated industrial parts. More particularly, the present invention relates to methods and systems for separating oil and dirt contamination from liquid cleaning medium circulated in a closed or partially closed flow loop.
Industrial cleaning solution is a descriptive phase that encompasses water-based alkaline cleaning solutions, acid cleaning solutions, lubricoolants, burnishing solutions and floor cleaning solutions. Such solutions are used in spray washes, dip tanks, steam cleaners, pressure washers and machine cutting tool coolant systems.
System volumes may range from a few gallons circulated at a half gallon per minute to tens of thousand of gallons circulated at hundreds of gallons per minute. A primary function of the circulated solution is to dissolve or emulsify oils and dislodge particles for flush removal. Consequently, water-based solutions are highly alkaline (caustic) solutions of emulsifier, surfactant and wetting agent.
Traditionally, the fluid circulation medium formulated for these industrial systems included inexpensive alkalis, surfactants, wetting agents and solvents. Little or no effort was made to filter or strip these solutions of accumulated contaminants. When saturated or contaminated to a predetermined degree, the solution charge was merely sewered and replaced with an entirely fresh make-up.
Under present regulations and standards of social accountability, many of the traditional solution make-up and contamination compounds are considered toxic and/or hazardous and are no longer accepted by public waste disposal facilities. The cost of private disposal has therefore steadily risen to the point the value of production waste disposal is a significant percentage of the product. Moreover, generators and transporters of toxic and hazardous waste are exposed to immense public liability in the event of public sector accidents and spills.
Due to increased composition and disposal costs, cleaning solution users have tended to hold and cycle a solution charge for longer time periods. If large sump tankage is available, some of the heavier, particulate contaminants will settle from the mixture. By keeping a solution circulating for more extended periods, however, has exacerbated bacteriological contamination. Solution sump tanks have been known to gelatinize in a few hours as a massive bacteria culture.
State-of-the-art filtration of these cleaning solution systems has proven to be largely ineffective due to the synergistic cooperation of both, fine particle contamination in the presence of oil or oil-like substances. Individually, either would quickly stratify for reliable separation. Oil and other low density substances having a specific gravity of less than 1.0 would rise and accumulate on a pond surface for separation by decantation. Dirt, scale and other high density particles having a specific gravity of greater than 1.0 would fall to the bottom of a pond in disposition for normal sediment disposal. Jointly, however, a mixture of oil and finely divided particles tends to create a colloidal suspension in which the low density oil coats the high density dirt particles for a buoyantly neutral composite. Attempts to screen or filter this suspension are frustrated by the oil presence which quickly blinds and plugs the filter permeability.
It is, therefore, an object of the present invention to provide a method and physical system for separating suspended contaminants from individual cleaning and processing solutions.
Another object of the present invention is to provide a method and physical system for controlling the growth of bacteria in industrial cleaning and processing solutions.
Another object of the present invention is to track a method and apparatus for continuously removing oil and particle contamination from a circulating system of industrial cleaning or processing solution at a rate at least equal to the contamination influx.
Another object of the present invention is to teach a method and apparatus for segregating oil and particle contaminants from a colloidal mixture of such contaminants in an industrial cleaning or processing solution.